Tanaka Announces Replacement of Power Semiconductor Wire with Copper for Mass Production

May 28, 2012 by Jeff Shepard

Tanaka Denshi Kogyo K.K. announced that New Japan Radio Co., Ltd. has adopted Tanaka Denshi Kogyo’s "CHA" thick copper wire for wiring on aluminum electrodes of semiconductor chips manufactured by New Japan Radio. This has led to the establishment of what the companies say is the world’s first power semiconductor mass production technology using copper wire.

New Japan Radio has conducted research and development with the aim of providing high reliability and reducing the burden on the environment as product technologies for applications requiring high voltage and large currents, such as industrial equipment, electric vehicles (EV), hybrid vehicles (HV) and smart grid (next-generation power grid) power transmission. In particular, the company focused on the wiring technology in semiconductor packaging technology, and conducted research and development on adopting thick copper wire capable of supporting higher voltages and larger currents to replace the thick aluminum wire that is currently the mainstay wiring material for power devices. However, because it has generally been technically difficult to mitigate chip damage when directly placing thick copper wire on aluminum electrodes, this was an obstacle for mass production.

Upon introduction of the thick copper wire, New Japan Radio worked with Tanaka Denshi Kogyo and equipment manufacturer Ultrasonic Engineering Co., Ltd. to utilize wedge bonding technology to succeed in directly placing thick copper wire with a wire diameter of over 200 micrometers (a micrometer is a millionth of a meter) onto the aluminum electrodes of semiconductor chips, and established this as a mass production technology. Tanaka Denshi Kogyo’s "CHA" thick copper wire used by New Japan Radio was released in January 2012 as a replacement for the thick aluminum wire currently widely used as large-current semiconductor wiring material for power devices. Tanaka Denshi Kogyo can practically implement copper wire for power devices by using its special processing equipment and annealing equipment to enable the uniform placement of microcrystal grain, which had been difficult in simple copper wire processing.

The melting point of aluminum is low at 660°C, and it sometimes fuses due to large currents. Moreover, as copper has a higher electric resistance than aluminum, CHA can raise the electrical conductivity by approximately 40% compared to aluminum of the same wire diameter.

Features of the mass production technology

1. High reliability; able to reach over 5,000 cycles in temperature cycling tests

Industrial equipment and EVs need to guarantee operation at high temperatures, and more demanding temperature cycling test life than present is required. The results of temperature cycling tests by New Japan Radio confirmed that copper wire has a product life of over 5,000 cycles compared to 2,000 cycles of aluminum wire.

2. Contribution to reduction of the burden on the environment by reducing the use of the material

Because copper wire has a higher fusing point than aluminum wire and is possible to obtain the characteristics of aluminum wire with a wire diameter of 300 micrometers using copper wire with a wire diameter of 200 micrometers, the amount of material used can be reduced, which contributes to reducing the burden on the environment. Furthermore, whereas the thermal conductivity of aluminum is 238W/mK, the thermal conductivity of copper is higher at 397W/mK, enabling it to be used as a low-loss technology due to its excellent exoergic properties.

New Japan Radio will primarily apply this technology to power devices, and will actively conduct product development. Tanaka Denshi Kogyo would like to contribute continuously to the advancement of development of the technology as a good business partner of New Japan Radio.

More news and information regarding the latest developments in Smart Grid electronics can be found at Darnell’s SmartGridElectronics.Net.